牧区草地资源利用的三元化结构及其水问题

牧区草原生态的修复,必须对草地资源的利用实施三元化战略,三元化利用的关键是水资源的合理开发利用。脆弱的草原生态系统与水资源的关系致为密切,水资源的开发利用稍有不慎,就会导致草原生态系统的受损,必须以生态学的观点科学合理地配置和利用水资源。     

草原文化景观的退化机制——基于鄂尔多斯草原与坝上草原对比

文章辨析了草原退化与土地荒漠化2个概念,草原退化是由不合理的人类活动和脆弱的生态环境相互作用所造成的,最终演变为土地荒漠化。选取鄂尔多斯草原与坝上草原2个北方典型区域作为研究对象,概述其现状,两者均发生生态退化现象。从自然机制上说,自然气候、降水、土壤、植被、易发生的自然灾害、易发生的生物灾害等均是导致其退化的原因。鄂尔多斯草原和坝上草原的草原退化的人为原因表现出一致性,例如不合理的开垦土地,过度放牧、过度樵采及挖掘中药材,不合理的旅游资源开发和城镇工程建设等。退化机理表现为：自然地理因素决定了自然环境的脆弱性,人文地理因素进一步影响了自然环境的脆弱性,这样导致草原退化,反作用于人类生态系统,又进一步反作用于自然生态系统。因此,从草原退化演替规律、定牧的原则、制度几个方面进行讨论,文章认为草原畜牧业要想可持续发展,必须落实“以草定畜”与“草畜平衡”制度,实行划区轮牧、休牧和禁牧制度。     

牧区草地承包经营权流转及其对牧民生计的影响——以内蒙古草原牧区为例

牧区草地承包经营权流转,是伴随草原新三牧政策(休牧、禁牧、划区轮牧)实施、畜牧业增长方式转型、牧区产业结构调整、牧区剩余劳动力转移等过程集中出现,又事关牧区民生与构建和谐新牧区的一个崭新的重要研究命题。本研究阐明内蒙古牧区草地承包经营权流转现状与特征,指出伴随草地流转出现租赁期短、草畜平衡对草地流转限制等问题以及牧区草地流转动因与东中部土地流转不同、草地类型流转程度不同的特征。畜产品是牧民主要收入来源,草地流转价格低影响牧民增收、加大牧区剩余劳动力转移风险。在牧区调研的基础上,提出建立与完善草地承包经营权流转机制的政策建议。     

Disturbances in tallgrass prairie: local and regional effects on community heterogeneity

Community heterogeneity in tallgrass prairie was analyzed at regional and local levels to assess the effects of disturbances on community structure at different spatial scales. The sites were part of NASA's First ISLSCP Field Experiment (FIFE) in Kansas, and were located on grassland treatments that were undisturbed, and burned-only on Konze Prairie Research Natural Area, and grazed-only and grazed + burned on adjacent ranch land. Sites in grazed-only or grazed + burned treatments were less similar to each other, on a regional scale (15 × 15 km), than were burned-only or undisturbed sites. Grazing reduced the cover of dominant species, making space available for the establishment of immigrants from the region. Each site was different because of establishment by different species from the large regional species pool. At the local scale (0.1 ha), the most homogeneous treatments were those that were most heterogeneous at the regional scale. Undisturbed treatments at the local scale were the most heterogeneous compared to sites under other treatments. Therefore, regional responses to disturbances were more variable than local responses, and were not predictable from within-site analyses.     

中国西门塔尔牛——科尔沁(草原)型在扎鲁特旗的培育发展

扎鲁特旗中国西门塔尔牛－科尔沁（草原）型培育工作,经过多年的努力,取得了较好的经济效益和社会效益。良种母牛成年平均体高达129.9cm,平均体重达568.5kg;305天平均产奶量达3187.5kg,乳脂率4．21％;24月龄阉牛120天育肥平均日增重1369g,屠宰率55．76％,净肉率45．57％;总体经济效益投入产出比为1：4．24。     

Grazing Preferences and Vegetation Feedbacks of the Fire-Grazing Interaction in the Northern Great Plains

The fire-grazing interaction is well studied in mesic grasslands worldwide, but research is limited in semiarid systems. We examined the principal drivers and feedbacks of the fire-grazing interaction on the strength of cattle grazing selection, herbaceous biomass, crude protein, and vegetation structure and composition in two pastures in the Northern Great Plains. Cattle showed significant preference, use, and grazing utilization in recently burned patches that declined as time since fire increased. Cattle selection was driven by significantly increased crude protein in recent burns. Grazing utilization of 70% in patches with < 1 yr after fire established low herbaceous biomass, but the extent to which it was maintained varied with precipitation. Herbaceous biomass increased to nonburned levels 2 yr after fire, and crude protein decreased to nonburned levels 120 d after fire. Species composition was influenced primarily by site and year, though bare ground and litter were influenced by the fire-grazing interaction. Our data indicate that mixed-grass prairies of the Northern Great Plains are resilient to the fire-grazing interaction and that rest from grazing following fire is likely ecologically unnecessary. The use of the fire-grazing interaction is an alternative management strategy suitable for the Northern Great Plains, effectively increasing heterogeneity of grassland habitat.     

Establishing Wyoming Big Sagebrush in Annual Brome-Invaded Landscapes with Seeding and Herbicides

Seeding native plants into degraded grasslands presents major challenges. Often, seeded species fail to establish and areas become/remain dominated by unwanted plants. We combined herbicides and seeding in former coal mining fields dominated by exotic winter annual grasses (downy brome [Bromus tectorum L.] and Japanese brome [Bromus arvensis L.], hereafter “annual bromes”). The main interest was restoring Wyoming big sagebrush (Artemisia tridentata spp. wyomingensis [Beetle & A. Young] S.L. Welsh, hereafter “big sage”), a very difficult species to restore to North American grasslands. We tested the nonselective herbicide glyphosate and the grass-specific herbicide quizalofop. The summer following herbicide applications and seeding, annual brome cover in controls 22% (CI_95% 13%, 36%) was significantly greater (P < 0.03) than in glyphosate 11% (CI_95% 5%, 25%) and quizalofop 16% (CI_95% 7%, 35%) treatments. At Decker mine, glyphosate increased seeded big sage density (P < 0.04) from 0.76 (CI_95% 0.27, 2.11) to 3.05 (CI_95% 1.42, 6.56) plants ? m^-2 the second summer after seeding. Corresponding increases for Spring Creek mine were from 0.11 (CI_95% 0.03, 0.43) to 0.43 (CI_95% 0.13, 1.40) plants ? m^-2 (P < 0.04). These results were consistent across two experiments initiated in different years. In addition to big sage, our study’s seed mixes contained native grasses and forbs, and herbicide treatments tended to promote establishment of these plant groups. In annual brome-dominated areas of the northern Great Plains, conditions amenable to big sage seedling establishment do not appear entirely uncommon, and herbicides can increase establishment.     

Feasibility of Using Commercial Reagent Test Strips for Estimation of Blood Urea Nitrogen Concentrations in Captive Black-Tailed Prairie Dogs (Cynomys ludovicianus)

The black-tailed prairie dog (Cynomys ludovicianus) is a squirrel-like rodent (Sciuridae) that is used as an animal model for human gallbladder disease, as well as research on several viral and bacterial diseases. Prairie dogs are also prone to develop hepatobiliary diseases that can impair liver function. As a result, monitoring blood urea nitrogen (BUN) concentration or azotemia via low-volume blood samples with immediate test results can be clinically beneficial. In this study, blood samples were collected from captive black-tailed prairie dogs. The BUN analysis was performed in duplicate using a veterinary biochemistry analyzer and commercial reagent test strips. The indication of azotemia by the reagent test strips, when compared to plasma BUN results of prairie dogs with and without confirmed azotemia, had a sensitivity, specificity, positive predictive value, and negative predictive value of 100%, 95%, 71%, and 100%, respectively. Based on the results of this study, the reagent test strips provided a moderately accurate method of estimating the BUN concentration and high accuracy reporting both normal and azotemic black-tailed prairie dogs. Continued investigation into alternative point-of-care testing for prairie dogs is warranted, but standard blood chemistry analyzers should still be considered the most accurate method of BUN testing and azotemia determination for this species.     

SURGICAL MANAGEMENT OF PANCREATIC NODULAR HYPERPLASIA BY PARTIAL PANCREATECTOMY IN A BLACK-TAILED PRAIRIE DOG (CYNOMYS LUDOVICIANUS)

A 7.5-year-old male black-tailed prairie dog was presented for diarrhea of 3 weeks’ duration. Clinical examination revealed a multinodular mass in the left cranial quadrant of the abdomen that was confirmed with ultrasound. An exploratory laparotomy was performed and the majority of the mass and adherent spleen were removed. Histological diagnosis was severe pancreatic nodular hyperplasia associated with secondary pancreatitis and passive splenic congestion. The prairie dog recovered without complications. Three weeks following the surgical procedure, follow-up ultrasound showed no evidence of abnormal tissue in the pancreaticoduodenal area. Two months postsurgery, a follow-up computed tomographic scan revealed no significant abnormalities. No recurrence was noted 13 months following the mass removal. This article describes the diagnosis of pancreatic nodular hyperplasia in a prairie dog and successful treatment of complications arising from the condition by partial pancreatectomy.     

Natural N abundances in a tallgrass prairie ecosystem exposed to 8-y of elevated atmospheric CO2

After 8-y of elevated CO₂, we previously detected greater amounts of total soil nitrogen, suggesting that rates of ecosystem N flux into or out of tallgrass prairie had been altered. Denitrification and associative N fixation rates are the two primary biological processes that are known to control N loss and accumulation in tallgrass prairie soil. Therefore, our objective was to assess the natural abundance of plant and soil ¹⁵N isotopes as a cumulative index of potential change in efflux or influx of N into and out of the tallgrass prairie after 8-y of exposure to elevated CO₂. Aboveground plant delta ¹⁵N values of Andropogon gerardii were close to zero and more positive as a result of elevated CO₂, but whole-soil values at the 5-30 cm depth were significantly reduced (6.8 vs 7.3; P<0.05) under elevated CO₂-chamber (EC) relative to ambient CO₂- chamber (AC). Total, aboveground plant biomass, root-in-growth, extractable N, microbial biomass N, and soil pools collectively exhibited a range of delta ¹⁵N values from −2.8 to 7.3. Measurements of surface soil ¹⁵N indicate that a change in N inputs and outputs has occurred as a result of elevated atmospheric CO₂. In addition to possible changes in denitrification and N₂ fixation, other sources of N such as the re-translocation of N to the surface from deeper soil layers are needed to explain how soil N accrues in surface soils as a consequence of elevated CO₂. Our results support the notion that C accrual may promote N accrual, possibly driven by high plant and microbial N demand amplified by soil N limitation.